If the tissue sample is benign (not cancer), surgery may be avoided. (In some cases, however, even if the tissue sample is benign, an excisional biopsy (a surgical biopsy) may be needed to confirm the diagnosis.)

Drawbacks of core needle biopsy

One drawback of core needle biopsy is that the needle can miss a tumor and take a sample of normal tissue instead. This is most likely to occur when the biopsy is done without the help of breast ultrasound, breast MRI or stereotactic mammography.

If a tumor is missed, the biopsy will show cancer does not exist when in fact, it does. This is called a false negative result and delays diagnosis.